A Study on the Influence of Meteorological Conditions on Dissemination and Amplification of Japanese Encephalitis Virus (JEV) in the pig-mosquito-pig cycle
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概要
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Since 1967 the seroepidemiological surveillance of Japanese encephalitis virus (JEV) has been conducted by the hemagglutination inhibition test (HI) on serum samples collected from 6-month-old pigs at the Akita Central Slaughterhouse in Akita, Akita Prefecture. Only retrospective results, however, were obtained on the epidemic occurrence of JEV in the prefecture, where summer was very short and not hot enough to have a good effect on dissemination and amplification of JEV in the course of the pig-mosquito-pig cycle. Then a predictable method was used to estimate the positive rate of HI antibody against JEV in porcine sera indirectly from meteorological conditions. The results obtained are as follows.<BR>1) A meteorological equation of W= (T/10) <SUP>11</SUP>×10<SUP>-9</SUP>×R<SUP>1/9</SUP>×t<SUP>4</SUP>was derived by correlative analysis on each sum total of atmospheric temperature (T), rainfalls (R), and 25C values (t) from the middle of July to the middle of August, and HI-positive rates (y) measured annually in porcine sera over a period from the end of August to October in 1967-1980. Furthermore, a regression equation of Y=0.08x+5.80 was obtained by regression analysis that had been done on y and x values (x= (W/Wm) ×100, Wm: mean) calculated with the Wequation by year. It was assumed to be a predictive equation to estimate HI-positive rates in porcine sera pro-spectively. Of fifteen HI-positive rates determined over a period from 1967 to 1980, eleven (73.3%) were within the Y±95% confidence limit. The value of×=100 was interpreted as a value giving warning to an epidemic of JEV; that is, it was assumed to indicate that the prevalence of JEV might occur.<BR>2) Fourteen predictive equations were derived successively under varying conditions of three factors which had constructed the meteorological equation. When they were examinned, the results obtained were not always satisfactory, but it was assumed that these equations might be able to predict the positive rate of HI antibody against JEV prospectively.
- 獣医疫学会の論文
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